Comparative analysis of growth and movements of the aboveground parts in some deciduous woody species

Vertical projections of nutation movements in the epicotyls of sessile oak, Turkey oak, horse chestnut and hypocotyls of European beech were recorded by means of photography and time-lapse cinematography at the early stages of their ontogeny. Attention was paid to the kinetics of growth rate, diameter of the lower part of the elongating zone, and the form, amplitude and frequency of nutation turns. At the beginning of ontogeny the vertical projection of the movements of all woody species under study was represented by irregular curves, followed by elliptical trajectories, particularly when reaching the maximum growth rate. The highest average growth rate was recorded in horse chestnut, followed by oak, and the lowest values were exhibited by beech. As to the size of amplitudes opposite results were obtained. The frequency of turns proved to be a less sensitive parameter characterizing the movement. It is suggested that the geocontrol system of horse chestnut is more effective than that of oak and, especially, of beech.     

Climate change effect on Betula (birch) and Quercus (oak) pollen seasons in the United States

Climatic change is expected to affect the spatiotemporal patterns of airborne allergenic pollen, which has been found to act synergistically with common air pollutants, such as ozone, to cause allergic airway disease (AAD). Observed airborne pollen data from six stations from 1994 to 2011 at Fargo (North Dakota), College Station (Texas), Omaha (Nebraska), Pleasanton (California), Cherry Hill and Newark (New Jersey) in the US were studied to examine climate change effects on trends of annual mean and peak value of daily concentrations, annual production, season start, and season length of Betula (birch) and Quercus (oak) pollen. The growing degree hour (GDH) model was used to establish a relationship between start/end dates and differential temperature sums using observed hourly temperatures from surrounding meteorology stations. Optimum GDH models were then combined with meteorological information from the Weather Research and Forecasting (WRF) model, and land use land coverage data from the Biogenic Emissions Land use Database, version 3.1 (BELD3.1), to simulate start dates and season lengths of birch and oak pollen for both past and future years across the contiguous US (CONUS). For most of the studied stations, comparison of mean pollen indices between the periods of 1994–2000 and 2001–2011 showed that birch and oak trees were observed to flower 1–2 weeks earlier; annual mean and peak value of daily pollen concentrations tended to increase by 13.6 %–248 %. The observed pollen season lengths varied for birch and for oak across the different monitoring stations. Optimum initial date, base temperature, and threshold GDH for start date was found to be 1 March, 8 °C, and 1,879 h, respectively, for birch; 1 March, 5 °C, and 4,760 h, respectively, for oak. Simulation results indicated that responses of birch and oak pollen seasons to climate change are expected to vary for different regions.     

Short photoperiod reduces the temperature sensitivity of leaf‐out in saplings of Fagus sylvatica but not in horse chestnut

Leaf phenology is one of the most reliable bioindicators of ongoing global warming in temperate and boreal zones because it is highly sensitive to temperature variation. A large number of studies have reported advanced spring leaf‐out due to global warming, yet the temperature sensitivity of leaf‐out has significantly decreased in temperate deciduous tree species over the past three decades. One of the possible mechanisms is that photoperiod is limiting further advance to protect the leaves against potential damaging frosts. However, the “photoperiod limitation” hypothesis remains poorly investigated and experimentally tested. Here, we conducted a photoperiod‐ and temperature‐manipulation experiment in climate chambers on two common deciduous species in Europe: Fagus sylvatica (European beech, a typically late flushing species) and Aesculus hippocastanum (horse chestnut, a typically early flushing species). In agreement with previous studies, we found that the warming significantly advanced the leaf‐out dates by 4.3 and 3.7 days/°C for beech and horse chestnut saplings, respectively. However, shorter photoperiod significantly reduced the temperature sensitivity of beech only (3.0 days/°C) by substantially increasing the heat requirement to avoid leafing‐out too early. Interestingly, the photoperiod limitation only occurs below a certain daylength (photoperiod threshold) when the warming increased above 4°C for beech trees. In contrast, for chestnut, no photoperiod threshold was found even when the ambient air temperature was warmed by 5°C. Given the species‐specific photoperiod effect on leaf phenology, the sequence of the leaf‐out timing among forest tree species may change under future climate warming conditions. Nonphotoperiodic species may benefit from warmer springs by starting the growing season earlier than photoperiodic sensitive species, modifying forest ecosystem structure and functions, but this photoperiod limitation needs to be further investigated experimentally in numerous species.     

Role of man in the history of vegetation of the Ellero valley (maritime Alps, Italy)

The pollen analysis of a sediment core from a peat bog (Rifugio Mondovi) at the mountain belt (1760 m) in the Ellero Valley (Italian Maritime Alps) shows the postglacial vegetation history. The sequence starts at 12,000 BP during a peak of pine pollen; this first phase shows a low representation of birch and the presence of Tilia. Younger Dryas is characterised by increasing percentages of Artemisia, showing the presence of deciduous Quercus, fir and beech. Elm appears at the beginning of the Holocene during the second pine peak (9800 BP). A 3000-year hiatus is present. Sedimentation resumes at 6000 BP in a Rhododendron fir-wood. The present timberline at 1500 m, at the limit of the beech wood, is a result of the decline of the fir-wood at 2600 BP, which allowed an expansion of beech. During this period, there was a continual increase in Gramineae and deciduous oak and the first occurrences of evergreen oak are observed. The development of larch occurs at 1800 BP, together with walnut, chestnut, cereals and vine.     

Stomata of trees growing in CO2-enriched air show reduced sensitivity to vapour pressure deficit and drought

Stomatal conductance ( g _s) and photosynthetic rate ( A ) were measured in young beech ( Fagus sylvatica ), chestnut ( Castanea sativa ) and oak ( Quercus robur ) growing in ambient or CO₂-enriched air. In oak, g _s was consistently reduced in elevated CO₂. However, in beech and chestnut, the stomata of trees growing in elevated CO₂ failed to close normally in response to increased leaf-to-air vapour pressure deficit (LAVPD). Consequently, while g _s was reduced in elevated CO₂ on days with low LAVPD, on warm sunny days (with correspondingly high LAVPD) g _s was unchanged or even slightly higher in elevated CO₂. Furthermore, during drought, g _s of beech and chestnut was unresponsive to [CO₂], over a wide range of ambient LAVPD, whereas in oak g _s was reduced by an average of 50% in elevated CO₂. Stimulation of A by elevated CO₂ in beech and chestnut was restricted to days with high irradiance, and was greatest in beech during drought. Hence, most of the additional carbon gain in elevated CO₂ was made at the expense of water economy, at precisely those times (drought, high evaporative demand) when water conservation was most important. Such effects could have serious consequences for drought tolerance, growth and, ultimately, survival as atmospheric [CO₂] increases.     

Climate and forest management affect 15N-uptake,N balance and biomass of European beech seedlings

We investigated the effect of (a) different local climate and (b) thinning of the forest canopy on growth and N status of naturally regenerated European beech seedlings in a beech forest on shallow rendzina soil in southern Germany. For this purpose, a ¹⁵N-tracing experiment was conducted during the growing season of the year 2000 with beech seedlings growing on a warm, dry SW-exposed site and a cooler, moist NE-exposed site, and in a thinned and a control stand at each site. Biomass, ¹⁵N uptake and partitioning and total N concentrations of beech seedlings were determined. Site and thinning produced clear differences, particularly at the end of the growing season. Biomass and cumulative ¹⁵N uptake of beech seedlings then increased due to thinning on the NE site and decreased on the SW site. Total N concentrations in leaves, roots and stems of beech seedlings responded similarly. Therefore, growth and N status of beech seedlings are found to be favoured by thinning under cool-moist conditions. However, under higher temperature and reduced water availability—conditions that are prognosticated in the near future—thinning reduces N uptake and plant N concentration and, thus, impairs N balance and growth of beech regeneration.     

中国东部温带植被生长季节的空间外推估计

利用地面植物物候和遥感归一化差值植被指数（NDVI）数据,以及一种物候-遥感外推方法,实现植被生长季节从少数站点到较多站点的空间外推。结果表明：（1）在1982～1993年期间,中国东部温带地区植被生长季节多年平均起讫日期的空间格局与春季和秋季平均气温的空间格局相关显著;（2）在不同纬度带和整个研究区域,植被生长季节结束日期呈显著推迟的趋势,而开始日期则呈不显著提前的趋势,这与欧洲和北美地区植被生长季节开始日期显著提前而结束日期不显著推迟的变化趋势完全不同;（3）北部纬度带的植被生长季节平均每年延长1．4～3．6d,全区的植被生长季节平均每年延长1．4d,与同期北半球和欧亚大陆植被生长季节延长的趋势数值相近;（4）植被生长季节结束日期的显著推迟与晚春至夏季的区域性降温有关,而植被生长季节开始日期的不显著提前则与晚冬至春季气温趋势的不稳定变化有关;（5）在年际变化方面,植被生长季节开始和结束日期分别与2～4月份平均气温和5～6月份平均气温呈负相关关系。     

Phenological responses of <Emphasis Type="Italic">Ulmus pumila</Emphasis> (Siberian Elm) to climate change in the temperate zone of China

Using Ulmus pumila (Siberian Elm) leaf unfolding and leaf fall phenological data from 46 stations in the temperate zone of China for the period 1986–2005, we detected linear trends in both start and end dates and length of the growing season. Moreover, we defined the optimum length period during which daily mean temperature affects the growing season start and end dates most markedly at each station in order to more precisely and rationally identify responses of the growing season to temperature. On average, the growing season start date advanced significantly at a rate of −4.0 days per decade, whereas the growing season end date was delayed significantly at a rate of 2.2 days per decade and the growing season length was prolonged significantly at a rate of 6.5 days per decade across the temperate zone of China. Thus, the growing season extension was induced mainly by the advancement of the start date. At individual stations, linear trends of the start date correlate negatively with linear trends of spring temperature during the optimum length period, namely, the quicker the spring temperature increased at a station, the quicker the start date advanced. With respect to growing season response to interannual temperature variation, a 1°C increase in spring temperature during the optimum length period may induce an advancement of 2.8 days in the start date of the growing season, whereas a 1°C increase in autumn temperature during the optimum length period may cause a delay of 2.1 days in the end date of the growing season, and a 1°C increase in annual mean temperature may result in a lengthening of the growing season of 9 days across the temperate zone of China. Therefore, the response of the start date to temperature is more sensitive than the response of the end date. At individual stations, the sensitivity of growing season response to temperature depends obviously on local thermal conditions, namely, either the negative response of the start date or the positive response of the end date and growing season length to temperature was stronger at warmer locations than at colder locations. Thus, future regional climate warming may enhance the sensitivity of plant phenological response to temperature, especially in colder regions.     

Effects of recent climate trends on the distribution of potential natural vegetation in Central Germany

Introducing climate quotients for the growing season (Q_gs) provides a way to quantify effects of climate trends with respect to Potential Natural Vegetation (PNV), especially beech forests (Fagus sylvatica L.) in Central Germany. What is crucial in this regard is the great influence of the dominant decrease in the amount of precipitation (up to 40% in the last 50 years) during the growing season versus the dormant season. However, precipitation during the dormant season (which is predominantly increasing: up to 40% in the last 50 years) is also important for replenishing the soil water supply. The Q_gs values of the Climatic Normal period of 1971–2000 are generally higher (up to 12% in lowland areas) compared with the Climatic Normal period of 1961–1990, the extent of the difference being in general inversely proportional to elevation above sea level. What this means for the area under investigation is that humidity conditions, which generally improve as the elevation above sea level increases, have a positive effect on the site potential. However, a comparison of the climatologically important period of 1991–2003 with the period of 1961–1990 (area-wide increase between 12% and 16%) could not identify this positive effect of elevation on precipitation for the area under investigation. With regard to the recent climate-based trends of PNV, we have shown that all natural spatial units in Central Germany are affected by progressing continentality (i.e., dryness) during the growing season and the resulting deterioration of the site potential. The area of potential beech forest at lower elevation has decreased in favour of oak forest as PNV, while less change is observed in the montane area.     

Castle Pišece,Slovenia – Building history and wood economy revealed by dendrochronology,dendroprovenancing and historical sources

Castle Pišece, located in SE Slovenia near the border with Croatia, is thought to have been built in the 12th/13th century as one in the line of Salzburg fortresses on the then SE border of the Holy Roman Empire. During thorough restoration that started in 2005, its wooden constructions became accessible for dendrochronological investigations. We collected representative samples from floor or ceiling constructions in most of the rooms in the castle. Dendrochronology helped us to identify felling dates of wood and to propose probable years of reconstructions in 1515, 1578, 1644, 1697, 1752, 1758, 1775 and 1878. The dating showed that the constructions in the presumed Romanesque and Renaissance parts of the building were not as old as expected, whereas those in the supposedly Baroque part of the castle were older than assumed. The selection of wood species used for constructions varied over time. Constructions with end dates 1515–1697 were made of oak (Quercus petraea and Q. robur), those dated to 1752 of silver fir (Abies alba), those dated to 1758 of sweet chestnut (Castanea sativa) and those dated to 1878 of common beech (Fagus sylvatica). Comparison of forestry archives and vegetation in the area showed that most of the timber could have originated from nearby forests; only silver fir had to be transported from sites that were at least 20 km away from the castle. Cross-dating of tree-ring series of oak elements with two reference chronologies from Slovenia and two from Austria confirmed the great likelihood that the wood used mostly originated from Slovenia. This indicates that dendroprovenancing, not used in the area before, could also be used SE of the Alps. Both the existing archival documents and dendrochronology indicate that woodworks have taken place every few decades in some periods. The dendrochronological dates can be partly linked to reports on earthquakes (especially the devastating one in 1511), rebellions and year marks carved on the stone plaques.     

Spatial and temporal variation of phenological growing season and climate change impacts in temperate eastern China

Using phenological and normalized difference vegetation index (NDVI) data from 1982 to 1993 at seven sample stations in temperate eastern China, we calculated the cumulative frequency of leaf unfolding and leaf coloration dates for deciduous species every 5 days throughout the study period. Then, we determined the growing season beginning and end dates by computing times when 50% of the species had undergone leaf unfolding and leaf coloration for each station year. Next, we used these beginning and end dates of the growing season as time markers to determine corresponding threshold NDVI values on NDVI curves for the pixels overlaying phenological stations. Based on a cluster analysis, we determined extrapolation areas for each phenological station in every year, and then implemented the spatial extrapolation of growing season parameters from the seven sample stations to all possible meteorological stations in the study area. Results show that spatial patterns of growing season beginning and end dates correlate significantly with spatial patterns of mean air temperatures in spring and autumn, respectively. Contrasting with results from similar studies in Europe and North America, our study suggests that there is a significant delay in leaf coloration dates, along with a less pronounced advance of leaf unfolding dates in different latitudinal zones and the whole area from 1982 to 1993. The growing season has been extended by 1.4–3.6 days per year in the northern zones and by 1.4 days per year across the entire study area on average. The apparent delay in growing season end dates is associated with regional cooling from late spring to summer, while the insignificant advancement in beginning dates corresponds to inconsistent temperature trend changes from late winter to spring. On an interannual basis, growing season beginning and end dates correlate negatively with mean air temperatures from February to April and from May to June, respectively.     

Bayesian calibration of the Unified budburst model in six temperate tree species

Numerous phenology models developed to predict the budburst date of trees have been merged into one Unified model (Chuine, 2000, J. Theor. Biol. 207, 337–347). In this study, we tested a simplified version of the Unified model (Unichill model) on six woody species. Budburst and temperature data were available for five sites across Belgium from 1957 to 1995. We calibrated the Unichill model using a Bayesian calibration procedure, which reduced the uncertainty of the parameter coefficients and quantified the prediction uncertainty. The model performance differed among species. For two species (chestnut and black locust), the model showed good performance when tested against independent data not used for calibration. For the four other species (beech, oak, birch, ash), the model performed poorly. Model performance improved substantially for most species when using site-specific parameter coefficients instead of across-site parameter coefficients. This suggested that budburst is influenced by local environment and/or genetic differences among populations. Chestnut, black locust and birch were found to be temperature-driven species, and we therefore analyzed the sensitivity of budburst date to forcing temperature in those three species. Model results showed that budburst advanced with increasing temperature for 1–3 days °C⁻¹, which agreed with the observed trends. In synthesis, our results suggest that the Unichill model can be successfully applied to chestnut and black locust (with both across-site and site-specific calibration) and to birch (with site-specific calibration). For other species, temperature is not the only determinant of budburst and additional influencing factors will need to be included in the model.     

Serological Comparison of Isolates of Cherry Leaf Roll Virus from Diseased Beech and Birch Trees in a Forest Decline Area in Germany with Other Isolates of the Virus

Abstract Two isolates of cherry leaf roll virus (CLRV), one from diseased beech and one from diseased birch trees in an area with forest decline near Bonn in West Germany, were found to be serologically closely related, but not indentical as assessed by spurformation of precipitin lines in agarose gel double diffusion tests. Such tests also distinguished these German CLRV isolates from ten other distinct CLRV isolates obtained from different natural hosts and from various countries. The German beech isolate was most similar serologically to isolates from walnut and from birch in England and the German birch isolate to an English cherry isolate and an isolate from Sambucus racemosa in Finland. These results provide further evidence of the antigenicdiversity of CLRV.     

Integration of flowering dates in phenology and pollen counts in aerobiology: analysis of their spatial and temporal coherence in Germany (1992–1999)

We studied the possibility of integrating flowering dates in phenology and pollen counts in aerobiology in Germany. Data were analyzed for three pollen types (Betula, Poaceae, Artemisia) at 51 stations with pollen traps, and corresponding phenological flowering dates for 400 adjacent stations (< 25 km) for the years 1992–1993 and 1997–1999. The spatial and temporal coherence of these data sets was investigated by comparing start and peak of the pollen season with local minima and means of plant flowering. Our study revealed that start of birch pollen season occurred on average 5.7 days earlier than local birch flowering. For mugwort and grass, the pollen season started on average after local flowering was observed; mugwort pollen was found 4.8 days later and grass pollen season started almost on the same day (0.6 days later) as local flowering. Whereas the peak of the birch pollen season coincided with the mean flowering dates (0.4 days later), the pollen peaks of the other two species took place much later. On average, the peak of mugwort pollen occurred 15.4 days later than mean local flowering, the peak of grass pollen catches followed 22.6 days after local flowering. The study revealed a great temporal divergence between pollen and flowering dates with an irregular spatial pattern across Germany. Not all pollen catches could be explained by local vegetation flowering. Possible reasons include long-distance transport, pollen contributions of other than phenologically observed species and methodological constraints. The results suggest that further research is needed before using flowering dates in phenology to extrapolate pollen counts.     

An analysis of relationships among plant community phenology and seasonal metrics of Normalized Difference Vegetation Index in the northern part of the monsoon region of China

This study focuses on relationships between the phenological growing season of plant communities and the seasonal metrics of Normalized Difference Vegetation Index (NDVI) at sample stations and pixels overlying them, and explores the procedure for determining the growing season of terrestrial vegetation at the regional scale, using threshold NDVI values obtained by surface–satellite analysis at individual stations/pixels. The cumulative frequency of phenophases has been calculated for each plant community and each year in order to determine the growing season at the three sample stations from 1982 to 1993. The precise thresholds were arbitrarily set as the dates on which the phenological cumulative frequency reached 5% and 10% (for the beginning) and 90% and 95% (for the end). The beginning and end dates of the growing season were then applied each year as time thresholds, to determine the corresponding 10-day peak greenness values from NDVI curves for 8-km² pixels overlying the phenological stations. According to a trend analysis, a lengthening of the growing seasons and an increase of the integrated growing season NDVI have been detected in the central part of the research region. The correlation between the beginning dates of the growing season and the corresponding threshold NDVI values is very low, which indicates that the satellite-sensor-derived greenness is independent of the beginning time of the growing season of local plant communities. Other than in spring, the correlation between the end dates of the growing season and the corresponding threshold NDVI values is highly significant. The negative correlation shows that the earlier the growing season terminates, the larger the corresponding threshold NDVI value, and vice versa. In order to estimate the beginning and end dates of the growing season using the threshold NDVI values at sites without phenological data from 1982 to 1993, we calculated the spatial correlation coefficients between NDVI time-series at each sample station and other contiguous sites year by year. The results provide the spatial extrapolation area of the growing season for each sample station. Thus, we can use the threshold NDVI value obtained at one sample station/pixel for a year to determine the growing season at the extrapolation sites with a similar vegetation type for the same year. Received: 25 October 2000 / Revised: 19 June 2001 / Accepted: 19 June 2001     

Isolation and expression of Lea gene in desiccation-tolerant microspore-derived embryos in Brassica spp

Seedlings of four deciduous tree species maple ( Acer pseudoplatanus ), beech ( Fagus sylvatica ), horse chestnut ( Aesculus hippocastanum ) and lime ( Tilia cordata ) were exposed to de-icing salt (NaCl) either through the soil or applied to the above ground plant parts. A soil solution of 1.65 g l⁻¹ NaCl was maintained from the start of the experiment in January 1999 until termination in June 1999. The main effects caused by salt treatment through the soil were a reduction in photosynthesis of up to 50% and the development of leaf chlorosis or necrosis covering up to 50% of the total leaf area for the most sensitive species (lime and beech); maple and horse chestnut were relatively tolerant. There was no significant correlation between Cl or Na concentration in leaves and the relative sensitivity of the species. Saturated salt solution was applied to bark, buds or leaf scars on two occasions three weeks apart during the winter season. This affected the timing of bud break with delays of up to eight days compared with the controls. In the most sensitive species the above ground salt treatments partly prevented bud break (beech) or reduced photosynthesis (lime). Uptake through the bark was most important for the development of stress effects, compared with uptake through the other above ground plant parts.     

近20年青藏高原东北部禾本科牧草生育期变化特征

利用1988—2010年青藏高原东北部地区5个站点牧草生育期地面观测数据,分析了近20年代表性牧草返青、开花、黄枯期及生长季的变化趋势,并通过偏相关分析探讨了气温和降水对牧草生育期的关系。结果表明,近20年青藏高原东北部牧草生育期北部推迟南部提前的特征明显。南部的三江源区域返青、开花与黄枯期总体呈显著提前趋势,其中曲麻莱羊茅返青期提前的倾向率达到-4 d/10 a,开花期为-13 d/10 a,黄枯期达到-9 d/10 a,且均通过0.01的显著性检验水平。北部环青海湖区域的海北西北针茅生育期则表现出一定的推迟趋势。生长季长度北部地区延长,而南部除甘德(垂穗披碱草)外均呈明显缩短趋势。近20 a黄枯期的变化幅度明显大于返青期,使得生长季长度的变化更多地受黄枯期变化的影响。1月和3月气温是影响研究区牧草返青最主要的气候因子,气温增高返青提前。开花期南北差异明显,北部与同期气温呈明显负相关关系,南部则主要与开花前2—3个月的降水量密切相关,降水增多大部地区开花期提前。此外,降水也是各地牧草黄枯的主要影响因子。     

Modelling relation of first shoot emergence in various tree species to meteorological parameters in Slovenia

The relation of first shoot emergence in various tree species (birch, beech, oak and spruce) to meteorological parameters was studied on the basis of phenological and meteorological observations at five locations in Slovenia during 1967–1986. A physical model was developed using tree branch temperature obtained by the energy balance equation. The gained linear dependence of first shoot emergence on effective tree branch temperature was compared with the results obtained by multiple regression analysis among first shoot emergence, effective temperature, global radiation, wind velocity and precipitation. A new method was developed to define the proper biological temperature threshold which was used for effective temperature calculations. Results of the physical model and of the multiple regression analysis are statistically significant and give similar correlations between first shoot emergence and meteorological parameters.     

Measuring and modelling plant area index in beech stands

For some beech (Fagus sylvatica L.) stands with different stand densities the plant area index (PAI) was measured by means of a Licor LAI-2000 plant canopy analyser. The stands are located on the slopes of a valley in south-west Germany and had been treated by different types of silvicultural management (heavy shelterwood felling, light shelterwood felling, control plot). The analyser was used (a) to investigate the light conditions on plots of the same thinning regime, (b) to quantify the differences between the different treatments and (c) to obtain absolute values of PAI for interdisciplinary research. PAI was measured at three different phenological stages (leafless, leaf-unfolding and fully leafed season in 2000) and was found to be about 5.2 for the fully developed canopy on the control plots, 3.2 on the light fellings and about 2.0 for the heavy fellings. In the leafless period PAI was between 1.1 (control) and 0.4 (heavy felling). Measurements made in summer 2000 and summer 2002 were compared, and showed an increase of PAI, especially on the thinned plots. Measurements of photosynthetically active radiation (PAR) above and below the canopy in combination with measured PAI were used to apply Beers Law of radiation extinction to calculate the extinction coefficient k for different sky conditions and for the different growing seasons on the control plots. The extinction coefficient k for the beech stands was found to be between 0.99 and 1.39 in the leafless period, 0.62 to 0.91 during leaf unfolding and between 0.68 and 0.83 in the fully leafed period. Using PAR measurements and the k values obtained, the annual cycle of PAI was modelled inverting Beers Law.     

Structure and Function of High Altitude Forests of Central Himalaya I. Dry Matter Dynamics

The present study deals with the structure and functioning ofthree different forest communities, viz., horse chestnut, silverfir and kharsu oak forests, in a high altitude region of CentralHimalaya. The tree density and total basal cover of horse chestnutforest was 280 and 76, silver fir forest 355 and 106, and kharsuoak forest 480 trees ha^-1 and 73 m² ha^-1, respectively. Allometricequations relating biomass of different tree components to cbh(circumference at breast height) were significant. Total vegetationbiomass was 505 t ha^-1 in horse chestnut, 566 t ha^-1 in silverfir and 593 t ha^-1 in kharsu oak forests, of which maximum contributionwas by tree layer followed by shrub, herb, sapling and seedlinglayers. The forest floor litter biomass was 2·1, 4·7and 4·2 t ha^-1 in horse chestnut, silver fir and kharsuoak forests, respectively. The total litter fall was 7·3,6·7 and 9·4 t ha^-1 year^-1, of which leaf littercontributed 48, 39 and 64% in horse chestnut, silver fir andkharsu oak forests, respectively. Turnover rate of tree litterwas 0·80 in horse chestnut, 0·61 in silver firand 0·71 in kharsu oak forests. Net primary productionof total vegetation was 19·6, 18·9 and 24·9t ha^-1 year-1, of which tree layer contributed maximum proportionfollowed by herb, shrub, sapling and seedling layers. To showdry matter storage and flow of dry matter within the system,compartment models were developed for all forests.Copyright1995, 1999 Academic Press Total basal cover, biomass, productivity, Quercus, Aesculus, Abies, high altitude, litter, compartmental transfer